He is keeping his supporters updated with regular posts online. In one, he said: “I may put on a brave face and appear to be positive, but I go through the fear, the sadness, and the despair, which are oft-times overwhelming, bringing me down to my knees – literally.”

Mr Haque has been attending community centres and mosques daily, raising money for his own treatment after he was told that the NHS, or the Cancer Drug Fund, will not pay for it.

Pembrolizumab – also known as keytruda – is a type of immunotherapy that stimulates the body’s immune system to fight cancer cells.

The NHS decision not to fund it is believed to be a “cohort decision”, which is when a drug is not recommended by the NHS in case it would lead to many other people demanding the same.

Mr Starmer, who was elected MP for Holborn and St Pancras in May last year. In his letter to Mr Hunt, Mr Starmer added: “The result is that Mr Haque is now in the invidious position of raising money for himself to pay for this treatment. At an estimated £6,500 every three weeks, this is putting huge financial and emotional strain on Mr Haque.”

Mr Starmer said he had been struck my Mr Haque’s “courage and dedication” adding: “I am sure you will agree that this is profoundly regrettable and unacceptable that anyone should have to fund potentially life-saving treatment in this way.”

Mr Starmer has received a letter from Mr Haque’s oncologist, Professor John Bridgwater, confirming that UCLH has had an “individual funding request” for another patient for the treatment denied, and “consequently a new funding request has not been submitted” for Mr Haque. The letter added that it had been made clear that “UCLH should not submit another application for this treatment”.

The drug is “licensed” for NHS patients with melanoma cancers but not for colorectal cancer, like Mr Haque, despite it being approved by the FDA in the US. It was on the back of America’s approval of the drug, and new research showing its benefits, that Professor Bridgwater made the application.

NHS England said: “We have looked into this one and pembrolizumab does not currently have a UK licence for the treatment of colorectal cancer and we have no record of an individual funding request.”

On Sunday, Mr Haque ran a stall at the annual Camden Mela in Coram’s Fields, where he raised £725.15. He said his first sessions of the drug had caused “a lot of pain”, but that his “energy was up and his pain has eased, and I’m sleeping a lot better – which are all good signs”.